1. Field of the Invention
This invention relates to aerosol valves used in aerosol dispensers containing water/alcohol systems. More specifically, the invention relates to such aerosol valves having plastic parts of a plastic which is not degraded over time in use with such water/alcohol systems.
2. Description of Related Art
FIG. 1 shows an aerosol valve in centerline section. The valve shown is of the type commonly used in dispensing deodorants, hair spray, bug sprays and so forth. It comprises a valve body 12 which is crimped into the pedestal of a mounting cup 14 of a metal container (shown only partially). Disposed between the valve body 12 and the top of the mounting cup pedestal is a gasket 18 having its opening aligned with a hole in the top of the pedestal. A valve stem 20 is provided and comprises a tubular upper part 21 which extends through the gasket and has a lower head section 22 which normally is driven by a spring 23 to seat on the gasket 18 closing off the port 24 through the tubular part 21. The lower end of the valve body 12 is formed with a tailpiece 26 which is connected to a dip tube 28 extending down into the liquid in the container.
An actuator button 28 fits snugly on the top of the upper part 21 of the stem as shown. It is provided with an orifice 30 through which the product is dispensed. It may include a swirl chamber as is conventional.
In the prior art the valve body 12 and stem 20 have almost invariably been made of Nylon 6/6, a material which molds well and has stood up to the propellant/products system heretofore used. It has been the practice to add to the Nylon material a mold lubricant such as a stearate to facilitate the molding process.
With the new demands of the government agencies which require reduced use of volatile organic compounds (V.O.C.'s), the aerosol industry has had to turn its attention to the amount of alcohol (which is the product in a hair spray, for instance) and the propellant (a hydrocarbon). To reduce the percentage of this mix, the aerosol filler has had to add water to bring V.O.C.'s down to an acceptable level. This substitution has provided a satisfactory aerosol dispensing system for the most part, but there have been problems. Contrary to the experience with systems without water added, the industry has noted that with water/alcohol systems there has been a tendency for the port 24 in the stem or the orifice 30 in the button to occasionally clog with solids heretofore of unknown origin.
To attempt to ascertain the cause of the clogging, I took Nylon samples in the form of Nylon pellets and Nylon valve bodies and systematically soaked such samples in a jar containing a water/ethanol mixture. After a period of time, I removed the pellets and bodies and permitted the remaining liquid to evaporate in a petri dish. Surprisingly, I discovered a residue containing solid particles. From this I have concluded that the Nylon, over a period of time in the water/alcohol system, partly disintegrates. This discovery has, of course, led to the postulate that the clogging of the orifice in the actuator button in aerosol systems using a water/alcohol system has been caused by the disintegration of the Nylon.
In an effort to confirm correctness of the postulate and to specify an alternate plastic suitable for molding aerosol valve parts which would be moldable in production and not be susceptible to the aforesaid disintegration and breaking away of plastic crystals and tiny fragments, we have conducted experiments as described above on samples of various available plastic substitutes, soaking the samples in the water/alcohol system, removing the samples and noting the residue after evaporation of the liquid.